Toad - biology.

Toad - biology. Toad, group of froglike amphibians that are usually distinguished from frogs by the roughness of the skin, due to a large number of glandular tubercules, and by the shorter hind legs. In the tropics, where most anuran (members of the order comprising the frogs, toads, and tree toads) species occur, however, the differences are harder to determine, and some species could qualify as either toads or frogs. Toads are shy, usually nocturnal animals, hiding during the day in dark, damp places and hopping about at night in search of insects, grubs, slugs, worms, and other invertebrates. They are often brownish or grayish in color and have warty skin; a flat head; swollen parotid glands on the side of the neck behind the eyes; bright, jewel-like eyes with a transverse pupil; and slightly webbed toes. They are often stouter than frogs and cannot leap as far. The tongue of the toad is attached to the front of its mouth. The tongue is flicked forward from the mouth, and the sticky tip grasps the prey and carries it back to the mouth. Unlike most frogs, most toads do not have teeth. The tongue produces quantities of mucus to help in swallowing. All anurans blink when they swallow; and, because no bone exists between the eye and the mouth, the eye is pushed against the roof of the mouth, forcing the food further back. In temperate regions, toads hibernate in burrows. In spring they mate, and the females lay their numerous ova in pools in gelatinous strings 1.2 m (4 ft) or more in length. The tadpoles are smaller and darker than those of frogs and do not accomplish their transformation into terrestrial toads until autumn. One toad genus includes more than 200 different species. These are native to most of the major landmasses of the world except Greenland, Australia, New Guinea, and New Zealand, but they are most abundant in tropical regions. One of the largest species, the giant, or cane, toad of tropical America, measures about 20 cm (about 8 in) in length. It has been widely introduced in areas, such as Hawaii and Australia, where formerly no toads existed. Originally, it was thought that the toad would help control the can beetle and other pests in these areas; however, the giant toad has itself become a pest because it devours native wildlife. Another species, the American toad, ranges throughout most of eastern North America. The southern toad is common in the southeastern United States, and other species are found in the West. Two species found primarily in central and southwestern Europe are commonly referred to as midwife toads because the male carries and cares for the eggs after they have been laid in strings by the female (see Midwife Toad). Scientific classification: Toads belong to the order Anura of the class Amphibia. The genus that includes more than 200 species is Bufo of the family Bufonidae. The giant toad is classified as Bufo marinus. The American toad is classified as Bufo americanus and the southern toad as Bufo terrestris. Midwife toads make up the genus Alytes of the family Discoglossidae. Microsoft ® Encarta ® 2009. © 1993-2008 Microsoft Corporation. All rights reserved.